The report is intended to show how cannabis could disrupt pharmaceutical sales in key treatment areas including chronic pain, PTSD, sleep disorders, anxiety, epilepsy, and chemotherapy side effects

This Feb. 19, 2013, file photo, shows OxyContin pills arranged for a photo at a pharmacy in Montpelier, Vt.

If the United States legalized medical marijuana for conditions such as chronic pain, anxiety and seizures, cannabis could siphon more than $4 billion annually from the nation's pharmaceutical industry, a new study hypothesizes.

The report expected to be released Wednesday by New Frontier Data, a provider of data and analytics to cannabis businesses, is intended to show how cannabis could disrupt pharmaceutical sales in nine key treatment areas.

"Any opportunity for alternatives that could result in reduced pharmaceutical drug use might present a compelling point of discussion from a public policy standpoint," said John Kagia, executive vice president of industry analytics for the Washington, D.C.-based New Frontier.

With the backdrop of opioid use concerns and the simmering debates on health care reform and marijuana legalization, Kagia and fellow analysts sought to explore the idea of pharmaceutical substitution — people eschewing prescription drugs and using medical marijuana to treat certain ailments.